One of the recent advances in the field of non-benzenoid aromatics would be the chemistry of the extended cyclic cross-conjugated compounds derived by insertion of more complex conjugated π-electron system instead of the exo-double bond in fulvene-, fulvalene-, annulenone-, and oxocarbon-systems. Many physical and chemical properties of remarkable interest have been developed in these newly designed cross-conjugated variations. The present review deals with the chemistry of quinarenes, quinarenones, quinocarbons, and their hetero analogs which are the extended cyclic cross-conjugated π-electron systems comprising one or more quinonoid structures. The fundamental insights mentioned here would provide helpful suggestions for the molecular design of organic dyes, highly polarized compounds, electron acceptors or electron donors having a bright prospect of developing the new field of application to the optoelectronics, organic super conductors, and so on.
This article describes syntheses of some natural β-acyl acrylates utilizing three newly developed synthetic methods for β-acyl acrylates. The first one includes Lewis acid catalyzed condensation with electrophiles or oxidation of 2- (trialkylsiloxy) furans, followed by hydrolysis. The second one utilizes 1, 3-dipolar cycloaddition of nitrile oxides or silylnitronates to acrylates, and subsequent transformation of the products, 5-alkyloxycarbonylisoxazoles, to β-acyl acrylate. These two methods were applied to the syntheses of 16 - membered lactones, (±) -pyrenophorin and (±) -A 26771B. In the application of the second one, 1, 3-dipolar cycloaddition was used as a new macrocyclic ring closure method. The third one which utilizes oxidative ring cleavage of bicyclic enol ether was applied to the synthesis of 10-membered lactone, pyrenolide B.
Strongly nucleophilic organometallic compounds, such as organo-coppers and-lithiums, and powerful electrophiles, such as BF3 and AlCl3, are generally thought to be incompatible under normal, homogeneous reaction conditions. As a matter of course, it is anticipated that the two species can not co-exist together and undergo transmetallation reaction. To our surprise, however, RCu and BF3 are compatible at low temperature. RCu·BF3 and related organocopper-Lewis acid reagents exhibit new and unique reactivities and selectivities; activation in the conjugate addition; highly regio-, stereo-, and chemo-selective conjugate addition; very high asymmetric induction in the conjugate addition; regioselective alkylation of allylic derivatives; selective reaction towards carbonyl groups, imines, epoxides, aziridines, ethers, acetals, orthoformates, and pyridinium salts.
Recent topics on reactions of highly strained saturated polycyclic compounds have been reviewed, which include 1) one-electron-transfer initiated reactions by various means, 2) oxidative addition of transition metals into strained C-C bond and, hydrogen-metal exchange reactions, 3) nucleophilic C-C bond cleavage reactions, 4) reactions with carbenes, and 5) cycloaddition reactions with 1, 2, 4-triazoline-3, 5-diones.
In consideration of the flat-sheet structure known as a secondary structure of peptides and proteins, the self association of N-acyl α-amino acid derivatives may reasonably be expected to occur in non-aqueous media. To confirm the structure of dynamically formed molecular complexes, spectral studies of N-acetylvaline tert-butyl ester (1) in a carbon tetrachloride solution were carried out. A split of the amide NH resonance into two 1H nmr signals for the D and L enantiomers, termed self-induced non-equivalence, was observed when the solute was enantiomerically enriched in the solution. A concentration study of 1H and 13C-NMR showed the diastereomeric dimers, whose associative interactions are bidentate NH--O=C (ester) hydrogen bonds, to be in the enantiomeric solutions. Ir spectra confirmed the stability difference between the diastereomeric dimers by an external comparison of optically pure and racemic samples in the carbon tetrachloride solution. The association stereoselectivity of solute 1 was applied to the design of chromatographic phase systems. When racemic solute 1 is injected into a non-chiral silica gel column using mobile phase solvent containing chiral solute 1 as an additive component, the racemate should interact with chiral solute 1 added to the mobile phase solvent, while passing through the column, to form transient diastereomeric dimers as observed in solution, and be separated. Self association-induced resolution was confirmed experimentally using radiolabelled solute 1 and the radioactivity detection. Attempts were made to widen the scope of application involved in the hydrogen-bond association mode to chiral recognition through the development of other resolving agents. N-Acetylvaline tert-butylamide was found to separate the homologues of N-acyl α-amino acid esters. Tartaric esters and amides were found capable of separating a variety of enantiomeric compounds in non-aqueous media.
Macrocyclic polyamines are a new class of functional molecules. They show (1) special features of mode of their proton uptake; (2) uptake of biological polyanions (such as TCA cycle polycarboxylates, phosphate, ATP and carbonate) and of catechols (such as dopa and dapamine); (3) selective inclusion of some transition metal ions (e. g. CuII); (4) selective uptake of hard metal ions (e. g. MgII); (5) peptide-like functions to stabilize unusual oxiadtion state of metal ions (e. g. CuIII, NiIII); (6) superoxide dismutase-like activities by macrocyclic polyamine complexes; (7) heme-like O2-uptake and activation functions by metal complexes; and (8) functions of phenolate-coordinate heme enzymes. These newly discovered properties will prove to be useful for the future development of entirely new type of medicines, chemicals, catalysts and so on.
N-Trifluoromethyl-N-nitrosotrifluoromethanesulfonamide (TNS-Tf) has been developed as a unique and effective trifluoromethylating agent which has two reactive CF3 radicals in a molecule. It was found that TNS-Tf served as a useful reagent for trifluoromethylation of activated aromatics, mercaptans, disulfides, and a uridine dervative photochemically or thermally. It was also found that TNS-Tf reacted with activated copper suspended in a polar solvent at room temperature to give CF3-Cu complex which could convert aryliodides to CF3-aromatics in good yields.